* FIX: Ensure JsLocaleHelper to obly outputs up-to-date translations
The old implementation forgot to filter out deprecated
translations, causing these translations to incorrectly override the new
locale in the frontend.
This commit fills in the forgotten where clause, filtering only the
up-to-date part.
Related meta topic: https://meta.discourse.org/t/outdated-translation-replacement-causing-missing-translation/314352
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
